Method and system for storm water system heat exchange

ABSTRACT

A system and method for structure heating, ventilation, and air conditioning (HVAC) that uses a heat exchanger to transfer heat between the structure and a subsurface storm water discharge chamber system is disclosed. Coils for heat exchange are located in permanently collected runoff within a storm water chamber system beneath the frost line; the use of coils located within the retained runoff allows for improved heat exchange over coils placed within soil. Also described are a sensing device and feedback loop for HVAC control, to improve efficiency at ambient temperatures near the subsurface temperature.

[0001] This application claims priority to applicant's copendingprovisional application entitled “METHOD AND SYSTEM FOR STORM WATERSYSTEM HEAT EXCHANGE” having U.S. Ser. No. 60/108,890 filed Nov. 17,1998.

FIELD OF THE INVENTION

[0002] The present invention relates to use of a storm water system forheat exchange and more particularly to a method and system for using anunderground storm water system for heat exchange for building heating,ventilation, and air conditioning (HVAC).

BACKGROUND

[0003] Many buildings and other structures for which heating or coolingis needed provide temperature control using a closed loop system havinga heat exchanger. A heat exchanger requires for operation a source foradding or removing heat from the structure. A common source for addingor removing heat that is known in the art involves capture of geothermalenergy, which is the energy from the earth or temperature from theearth, using a heat exchanger.

[0004] The operation of a heat exchanger can be understood by referenceto the radiator of a car, which is one form of heat exchanger. In a car,heat from the engine is transferred to coolant circulated within theengine. The coolant is then pumped into a radiator, where heat istransferred to the surrounding air, and the cooled coolant is returnedto the engine to begin the cycle again. In this manner, heat istransferred from the engine so as to maintain the temperature of theengine below the boiling point.

[0005] A similar approach is used to cool a structure, such as abuilding. A heat exchanger connected to a building takes advantage ofthe temperature difference between the ambient or surface airtemperature and a constant temperature source, such as relativelyconstant subsurface temperature (subsurface temperature, as used herein,refers to the temperature at a depth of several feet below the surfaceof the earth, the depth of which depends on the climate and otherconditions of the area; below this set depth, the temperature is knownto generally remain constant). The heat exchanger is used to transferthe temperature difference from the subsurface area to the buildinglocated on the surface. Because the subsurface temperature is typicallyabove the surface temperature in Winter, heat may be transferred to thestructure via the heat exchanger to heat the structure, and because thesubsurface temperature is typically less than the surface temperatureduring the Summer, the heat exchanger can transfer the heat in thebuilding from the surface to the subsurface to cool the structure.

[0006] The relatively constant subsurface temperature of the earth iscommonly considered when laying water pipes or sewer pipes, as well aswhen building a structure. In these cases, it is often important thatthe pipes or structure be located below the frost line—the area withinthe ground below which water freezes. Ground below the frost line has atypically somewhat higher temperature than the ambient air temperatureat the surface in Winter, and typically somewhat lower temperature thanthe ambient air temperature at the surface in Summer.

[0007] It is known in the art to provide this heat exchange by diggingan excavation, referred to as a field, for the structure, planting aclosed loop heat exchanger in the earth for capturing or releasing heat.A problem with this approach is that the heat transfer coefficientbetween the coolant contained in the closed loop of the heat exchangerand the solid of the soil in which the loop is located is substantiallyless than the heat transfer coefficient for liquid-to-liquid or liquidto gas heat transfer. As a result, heat transfer using soil results ininefficiency compared to heat transfer using a liquid or gas.

[0008] For a completely unrelated reason to heat transfer, it is alsoknown in the art to provide subsurface storage of storm water forbusinesses and other developments, such as parking lots. These systemsare referred to as underground storm water chamber systems. Subsurfacestorage can include storage tanks specially designed and constructed forthese facilities, and storm water is also storable in above-groundconstructs, such as surface ponds or impoundments.

[0009] Underground storm water chamber systems can be either detentionsystems, retention systems, or first flush attenuation systems.Detention systems store a calculated volume of storm water in thechamber. Water is released at a predetermined rate to an outflowstructure. Retention systems also store a calculated volume of stormwater in the chamber; however, the primary drainage mechanism inretention systems is infiltration into the soil. First flush attenuationsystems are similar to retention systems; however, they have limitedcapacity. Once capacity has been met, excess storm water is releasedinto an outlet. First flush attenuation systems are often used to takeadvantage of the soil's filtration and renovation capabilities when theinital runoff contains a high percentage of pollutants. The presentinvention can be used in conjunction with any form of underground stormwater chamber system.

[0010] A storm water management system is designed for managing thedischarge of water from new construction so that the volume of waterthat leaves the site is no greater that the volume before theconstruction began. For example, if the site was a meadow with trees andgrass, typical runoff levels would be relatively small, such as tenpercent of the rainfall, with ninety per cent of the rainfall beingabsorbed into the ground. After construction on such a site, however,runoff may be much greater than it was when the site was a meadow.

[0011] Whenever new construction occurs or there are other improvementto property, in general, a calculation must be made to ensure thatsufficient runoff storage capacity for the geographical area isprovided, such that the base line of rainfall that is anticipated in thearea from historical data is maintained. The calculations for storagecapacity are predicated on the historical rainfall information, so thatthe storage capacity of the storm water management system will have thecapacity to contain the predicted amount of runoff that can be expectedwith the new construction or other improvement, and this capacitymaintained and metered out at the same rate of discharge that wasoccurring before the construction.

[0012] This discharge from the storm water system typically is made to astorm drain, which most municipalities and incorporated townships haveinstalled to keep water or storm water from collecting on the surface.In more rural areas, this discharge may typically occur onto neighboringproperty or into open swales or ditches along roadways. Municipalsystems that combine both sanitary and storm water systems typicallyfurther include backflow preventors installed from the storm watermanagement system, such that no sanitary effluent can back up into thesystem.

[0013] In order to accomplish the runoff collection and dischargeneeded, a typical storm water collection system collects runoff asquickly as possible. For example, the system might include athirty-six-inch pipe leading into the storm water management collectionarea to allow for significant inflow of runoff. The same system mightalso have only a four-inch diameter exit pipe to control the discharge.As a result, during a rainfall event, the system typically becomesinundated with runoff, which is then discharged at a lower flow ratethrough the exit pipe. Thus, the net effect of collected rainfall on theproperty during a rainfall event is that downstream receivers of thedischarge receive the same amount of water, which is metered out overtime, as was received prior to the new construction or otherimprovement.

[0014] Typical storm water management systems are further designed suchthat no runoff or only a small amount of runoff normally remains in thesystem. In these systems, the small amount of runoff typically remainsin the system solely for water quality management purposes. These waterquality management purposes, which are also unrelated to heat exchange,are generally mandated by the local water quality control authority,requiring that the quality of the water discharged from the storm watermanagement system be of the same quality as the rain water.

[0015] It is also known in the art to provide underground storage usingprefabricated units that are interlockable. An example of suchprefabricated units is the Maximizer Chamber System made by InfiltratorSystems Inc. of Old Saybrook, Conn. In this system, rows of individuallyprefabricated chambers are interlocked to form a continuous storagespace that is structurally tested to withstand high surface pressures,as from vehicles parked above the system.

[0016] Because underground storm water chamber systems are typicallylocated below the frost line, any water within these systems will reachan equilibrium temperature regardless of the seasonal air temperature atthe surface above the system. For the same reasons as described above,this equilibrium temperature is typically below the surface airtemperature during Summer and above the surface air temperature duringWinter.

[0017] There is a need for a method and system for utilizing theintrinsic heat properties of water stored in a storm water chambersystem for operation in conjunction with conventional HVAC systems ofstructures, such as buildings or other facilities, located near thestorm water chamber system to provide efficient heating and cooling ofthese structures. There is a further need to utilize a liquid-to-liquidor liquid-to-gas heat exchange for heating and cooling such facilitiesin conjunction with use of a storm water chamber system.

SUMMARY OF THE INVENTION

[0018] It is an advantage of the present invention to solve the problemsof the prior art by utilizing existing excavation made for otherpurposes to provide a location for a heat exchanger for a structure.

[0019] It is a further advantage of the present invention to provide amethod and system for utilizing the energy of water stored in a stormwater chamber system for operation with conventional HVAC systems ofbuildings or other facilities located near the storm water chambersystem to heat and cool these facilities.

[0020] It is a further advantage of the present invention to provide fora heat exchange system locatable within prefabricated storm waterchamber chambers. It is a further advantage of the present invention toprovide for an interlockable heat exchange system that is interlockablewith units of a storm water chamber system.

[0021] It is a further advantage of the present invention to provide fora method and system for retaining a minimum volume of water within astorm water chamber system having a heat exchange element, such that theheat exchange element remains immersed within retained runoff in thesystem.

[0022] It is a further advantage of the present invention to provide fora method and system for feeding back information from the storm waterchamber system to the heat exchange portion of an HVAC system of abuilding or other facility to increase the efficiency of the system.

[0023] An embodiment of the present invention utilizes the excavationfor a storm water management system to provide a source for capture ofgeothermal energy. This embodiment thereby uses a liquid-to-liquid orliquid-to-gas transfer ratio because the coil containing the liquid orgas medium of the heat exchanger is immersed in the liquid runoff thatis contained within the storm water management system.

[0024] An embodiment of the present invention includes a closed loopheat exchanger system having connections by, for example, pipescontaining a fluid or gas heat exchanger medium, and other components.The components of this embodiment include a pair of heat exchangerportions connected by a loop, and a pump that serves as a circulator forthe heat exchange medium. In an embodiment of the present invention, thecirculator moves the medium between an above ground heat exchanger, suchas a radiator, for example, located in a building, and a below groundheat exchanger that includes coils located within a storm water chambersystem. An embodiment of the present invention further includes asensing device, such as a thermocouple, and feedback loop for HVACcontrol, to improve efficiency at ambient temperatures near thesubsurface temperature.

[0025] Additional objects, advantages and novel features of theinvention will be set forth in part in the description that follows, andin part will become more apparent to those skilled in the art uponexamination of the following or upon learning by practice of theinvention.

BRIEF DESCRIPTION OF THE FIGURES

[0026] In the figures:

[0027]FIG. 1 depicts a perspective view of an example underground stormwater system heat exchange and HVAC system according to an embodiment ofthe present invention;

[0028]FIG. 2 shows a closeup perspective view of the storm water systemheat exchange component of an embodiment of the present invention;

[0029]FIGS. 3A and 3B present perspective views of two differentconfigurations of connected units of the storm water heat exchangecomponent of an embodiment of the present invention;

[0030]FIG. 4 presents a flow diagram of the storm water heat exchangerprocess of an embodiment of the present invention; and

[0031]FIG. 5 shows a closeup perspective view of one configuration ofthe storm water heat exchange component of an embodiment of the presentinvention.

DETAILED DESCRIPTION

[0032]FIGS. 1 and 2 illustrate an embodiment of the present inventionthat includes a closed loop heat exchanger system 1, 2 a, 2 b, 15 havingconnections by, for example, pipes containing a fluid or gas heatexchanger medium, and other components. The components of thisembodiment include a pair of heat exchangers portions 3, 15 connected bya loop 2 a, 2 b, and a pump 3 that serves as a circulator for the heatexchange medium. In an embodiment of the present invention, thecirculator 3 moves the medium between an above ground heat exchanger 3,such as a radiator, for example, located in a building 4, and a belowground heat exchanger 15 that includes coils located within a stormwater chamber system 1. The storm water chamber system I maintains acontinuous level of contained runoff 11. An embodiment of the presentinvention further includes a sensing device 16, which may include, forexample, a thermocouple, and feedback loop for HVAC control 5 to improveefficiency at ambient temperatures near the subsurface temperature.

[0033] When the base is pourous, it is more difficult to maintain acontinuous level of runoff between rains. FIG. 5 shows one embodiment ofthe present invention designed to capture runoff water 24 when the baseis unable to sufficiently retain a proper water level. Retaining walls23 capture and hold runoff water 24 when the water level rises above theretaining walls 23. When the water level falls back down due to theporous base, the captured runoff water 24 can still be used to increasethe efficiency of heat transfer. To minimize evaporation, water retainertops 22 are used to cover the captured runoff water 24. This embodimentcan also be used as additional reservoirs for pollutants to collect.

[0034] As discussed above, typical existing unit-type storm waterchamber systems are expandable and combinable. The units come in easilytransportable sections that are attachable together and may be assembledin the field, after excavation is completed. In accordance with anembodiment of the present invention, coil capacity for a heat exchangeris integrated into these units, such that the portions of the heatexchanger system may be similarly sectioned together.

[0035] In an embodiment of present invention, a coil, which is embeddedinto the system, is molded into the units of the system when made, andcertain fittings that allow the flexibility to terminate and to createloop conditions are included, such that the system may be expanded tothe size needed for the storm water management system. For example, toincrease the size of the system, a combination of fittings is used thatallows the system to be made longer, shorter, or wider, in whateverconfiguration that is needed.

[0036] In another embodiment of the present invention, the coil is woventhroughout the bottom of the storm water chambers providing increasestructural integrity by resisting spreading at the bottom of the stormwater chambers when extreme pressures are applied such as that caused byan automobile parking above a storm water chamber. Additionally, thecoil must be configured to prevent crimping when extreme pressures areplaced on the tubing.

[0037] Two configurations of connected units according to thisembodiment are shown in FIGS. 3A and 3B. In FIG. 3A, units 1 a, 1 b, 1 care connected lengthwise to provide a storm water management system heatexchanger component that has a rectangular shape, as viewed fromoverhead. In FIG. 3B, the units 1 a, 1 b, 1 c, 1 d are arranged so as toform a generally L-shaped storm water management system heat exchangercomponent, as viewed from overhead. Such a system can also include loopson the ends that are orientable in a left-handed or right-handeddirection, and ultimately leadable to a location where a supply line anda return line are attached.

[0038] In an embodiment of the present invention, rather thandischarging from the bottom or the lowest point of the storm watermanagement system, as is typical in the prior art, runoff is dischargedat a predetermined level, such that a permanent volume of runoff ismaintained in the system. For example, an embodiment of the presentinvention may include six feet of water permanently maintained in thebottom of the storm water management system. In this embodiment, thecoil of the heat exchanger is located at the bottom of the maintainedwater level, which allows the achievement of a higher transfer rate fromthe subsurface portion of the heat exchanger system than would occur ifthe heat exchanger used soil for the heat transfer.

[0039] As shown in FIG. 1, the system of an embodiment of the presentinvention includes units 1 made of a plastic material that arepremolded, joinable, and have sufficient strength to withstand vehiclesand other pressures from parking lots or other construction placed abovethe system. In a typical use of these units, they are connected to oneanother in a manner prescribed by the manufacturer such that the systemas a whole stores storm water in a fashion that is consistent with thelaws of the natural resources management authority, as described above.

[0040] In FIG. 1, a heat exchange system (shown in FIG. 2) within astorm water management system 1, having an inlet 12 and a storm drain16, is connected by a return line 2 a and a supply line 2 b to a heatexchanger and circulator unit 3 within a structure 4, such as abuilding. The circulator unit 3, which is located in the structure 4,operates in conjunction with the structure HVAC system 5.

[0041] In an embodiment of the present invention, runoff from thesurface 10 collects via the inlet 12 in the storm water managementsystem 1. The collected runoff in turn is released from the storm watermanagement system 1 to the storm drain 14, by, for example, reaching alevel 11 above the height of the outlet 16 for the storm drain 14. In anembodiment of the present invention, a predetermined volume of liquidfrom the collected runoff remains within the storm water managementsystem at this level 11.

[0042]FIG. 2 shows a closeup view of the subsurface storm water systemheat exchange component of an embodiment of the present invention. InFIG. 2, the permanent water level 11 is presented on the scale locatedon the right hand side of the figure, and the dotted line depicts thepermanent water level 11 within the system 1 for an embodiment of thepresent invention. Also shown is the loop of the heat exchanger 15,which is located below the permanent water line 11 retained within thesystem 1.

[0043] As shown in FIG. 2, an embodiment of the present inventionfurther includes a sensor 16 located within the storm water managementloop that feeds information back to the energy management system in thebuilding or other structure, such that optimal or otherwise morebeneficial times for operating the circulator for the heat exchanger maybe determined.

[0044] For example, at certain times, it may be determined that theambient air temperature is close to the temperature that is to bemaintained inside the structure. In this situation, the cost tocirculate the circulator could exceed the benefits of the relativelysmall fraction of temperature difference between the retained water andthe surface ambient temperature. The sensor is employed to feed backmonitoring information to an energy management portion of the system sothat the system only attempts to capture energy when it was suitable todo so.

[0045]FIG. 4 presents a flow diagram of the heating and coolingoperation of the heat exchange system in accordance with an embodimentof the present invention. As shown in FIG. 4, in step S1, a structureinternal temperature input is received. In step S2, a retained stormwater temperature input is received. In step S3, a selection of heatingor cooling is made. In step S4, a temperature comparison is made betweenthe structure internal temperature input and the retained storm watertemperature input.

[0046] In step S5, it is determined whether a selection for heating orcooling has been made. If heating is selected in step S5, the systemproceeds to step S6. In step S6, a determination is made as to whetherthe internal temperature is less than the retained storm watertemperature. If no in step S6, the system returns to step S4 fortemperature comparison. If yes in step S6, heat is transferred from thestorm water system heat exchanger to the structure heat exchanger, sothat the structure is heated.

[0047] In step S5, if cooling is selected, the system proceeds to stepS8. In step S8, a determination is made as to whether the internaltemperature is greater than the retained storm water temperature. If noin step S8, the system returns to step S4 for temperature comparison. Ifyes in step S8, heat is transferred from the structure heat exchanger tothe storm water system heat exchanger, so that the structure is cooled.

[0048] In one embodiment of the present invention, in step S3, aselection of heating or cooling is made based on the outdoor airtemperature. If the outdoor air temperature is cooler than the internaltemperature and cooling is desired, it is unnecessary to activate theprimary cooling system. Conversely, if the outdoor air temperature iswarmer than the internal temperature and heating is desired, it isunnecessary to active the primary heating system.

[0049] Embodiments of the present invention have now been described infulfillment of the above objects. It will be appreciated that theseexamples are merely illustrative of the invention. Many variations andmodifications will be apparent to those skilled in the art.

I claim:
 1. A system for providing heat conduction for a structure,comprising: a storm water management system located below a frost line,wherein a predetermined level of liquid is maintained within the stormwater management system; a first heat exchanger located within the stormwater management system, the first heat exchanger located such that thefirst heat exchanger is continuously immersed within the liquidmaintained within the storm water management system; a connecting lineconnected to the first heat exchanger; and a second heat exchangerconnected to the connecting line, wherein the second heat exchangerdirectly conducts heat with the structure; wherein the second heatexchanger transfers heat with the first heat exchanger via theconnecting line.
 2. The system of claim 1, further comprising a mediumfor heat exchange, the medium being contained by the first heatexchanger, the second heat exchanger, and the connecting line.
 3. Thesystem of claim 2, wherein the medium comprises one selected from thegroup consisting of a fluid and a gas.
 4. The system of claim 1, furthercomprising: a controller for controlling the heat transfer between thefirst heat exchanger and the second heat exchanger; and a selectorcoupled to the controller, the selector for receiving a selection fromthe group consisting of heating and cooling.
 5. The system of claim 4,further comprising: a valve for permitting heat transfer, the valvehaving at least a first position wherein heat is transferable betweenthe second heat exchanger and the first heat exchanger.
 6. The system ofclaim 4, wherein the structure has a structure internal temperature,wherein the liquid has a liquid temperature, and wherein if theselection is cooling and if the liquid temperature is less than thestructure internal temperature, heat is transferred from the second heatexchanger to the first heat exchanger.
 7. The system of claim 4, whereinthe structure has a structure internal temperature, wherein the liquidhas a liquid temperature, and wherein if the selection is cooling and ifthe liquid temperature is more than a predetermined temperature lessthan the structure internal temperature, heat is transferred from thesecond heat exchanger to the first heat exchanger.
 8. The system ofclaim 4, wherein the structure has a structure internal temperature,wherein the liquid has a liquid temperature, and wherein if theselection is heating and if the structure internal temperature is lessthan the liquid temperature, heat is transferable from the first heatexchanger to the second heat exchanger.
 9. The system of claim 1,wherein the storm water management system comprises a plurality ofunits, each of the plurality of units including section of the firstheat exchanger, such that a plurality of sections are included in theplurality of units.
 10. The system of claim 9, wherein the first heatexchanger has a variable size, the variable size varying by a number ofconnected sections of the plurality of sections.
 11. The system of claim1, wherein the second heat exchanger is connected to a heating,ventilation, and air conditioning system.
 12. The system of claim 1,wherein the structure comprises a building.
 13. The system of claim 1,wherein the storm water management system includes an inlet forreceiving liquid and an outlet for draining liquid.
 14. The system ofclaim 13, wherein the predetermined level of liquid within the stormwater management system is maintained by locating the outlet at a levelat least equal to the predetermined level.
 15. The system of claim 1,wherein the liquid comprises retained storm water.
 16. The system ofclaim 1, wherein the first heat exchanger, the connecting line, and thesecond heat exchanger form a loop for containing a heat exchange medium.17. The system of claim 9, wherein each of the plurality of units may beconnected to another of the plurality of units at a plurality ofpossible connection points.
 18. The system of claim 4, wherein theliquid has a liquid temperature, and wherein the storm water chambersystem includes a liquid temperature measuring device, the systemfurther comprising: a liquid temperature measuring device connectorconnected to the controller.
 19. The system of claim 4, wherein thestructure has a structure internal temperature, and wherein thestructure includes a structure internal temperature measuring device,the system further comprising: a structure internal temperaturemeasuring device connector connected to the controller; and a comparercoupled to the controller, the comparer for comparing temperatures. 20.The system of claim 2, further comprising a circulator for circulatingthe medium among the first heat exchanger, the connecting line, and thesecond heat exchanger.
 21. The system of claim 20, wherein thecirculator includes a pump.
 22. A method for providing heat conductionfor a structure using a storm water management system located below afrost line, the structure having a structure internal temperature, thestorm water management system containing a first heat exchanger andretaining a liquid, wherein the first heat exchanger is immersed in theliquid, the liquid having a liquid temperature; a connecting lineconnected to the first heat exchanger; and a second heat exchangerconnected to the connecting line, the second heat exchanger for directlyconducting heat with the structure, comprising: determining thestructure internal temperature; determining the liquid temperature;receiving a selection from the group consisting of heating and cooling;comparing the liquid temperature to the structure internal temperature;and determining whether to transfer heat between the second heatexchanger and the first heat exchanger.
 23. The method of claim 22,further comprising: if the liquid temperature is less than the structureinternal temperature and the selection is cooling, transferring heatfrom the second heat exchanger to the first heat exchanger.
 24. Themethod of claim 22, further comprising: if the liquid temperature isgreater than the structure internal temperature and the selection isheating, transferring heat from the first heat exchanger to the secondheat exchanger.
 25. The method of claim 22, wherein the storm waterchamber system further comprises a storm water chamber systemtemperature sensing device, and wherein determining the liquidtemperature comprises receiving data from the storm water chamber systemtemperature sensing device.
 26. The method of claim 25, wherein thestorm water chamber system temperature sensing device comprises athermocouple.
 27. The method of claim 22, wherein the structure furthercomprises a structure internal temperature sensing device, and whereindetermining the structure internal temperature comprises receiving datafrom the structure internal temperature sensing device.
 28. The methodof claim 22, wherein the selection is received from a user.
 29. Themethod of claim 22, wherein the first heat exchanger provides increasedstructural integrity to the structure.
 30. A method for providing heatconduction for a structure using a storm water management system locatedbelow a frost line, the storm water management system containing a firstheat exchanger and retaining a liquid, wherein the first heat exchangeris immersed in the liquid, the liquid having a liquid temperature; aconnecting line connected to the first heat exchanger; and a second heatexchanger connected to the connecting line, the second heat exchangerfor directly conducting heat with the structure, comprising: receiving aselection from the group consisting of heating and cooling; if theselection is heating, transferring heat from the second heat exchangerto the first heat exchanger, such that the structure is heated; and ifthe selection is cooling, transferring heat from the first heatexchanger to the second heat exchanger, such that the structure iscooled.